The present invention relates to a soil probing device. The present invention also relates to a method for performing a soil probing operation using such a soil probing device.
U.S. Pat. No. 5,902,939 discloses a soil probing device with a plurality of linkable rod sections for the assembly of a probing rod, which probing rod, while being pushed into the soil, is extendable each time by one or more rod sections. The probing device for example is provided with a clamp which grips the rod and can be pushed downwards by one or more associated hydraulic cylinders. While the probing rod section is being linked up, the process of pushing the probing rod into the soil can be temporarily stopped, but the probing process is preferably continued without interruption.
The known soil probing device further has a measuring probe which is fitted to the probing rod and is provided with measuring means to obtain data regarding the soil. The measuring probe can, for example, be a penetrometer comprising a cone for measuring the cone resistance, a friction sleeve for measuring side friction, and optionally sensors for measuring other parameters such as, for example, probe inclination, equilibrium water pressure, etc. Alternative designs of the probe are also possible, however.
The known soil probing device further has data transmission means which are designed for transmission of data between the measuring probe and a location at or near the soil surface.
In the known probing device the measurement data are transmitted from the probe via a umbilical cable running through the rod sections linked together from the measuring probe to the processing and recording apparatus at the surface. One or more fiber optical cable may form part of this umbilical cable for the optical transmission of measurement date. The use of such a continuous cable is inconvenient, however, when the rod sections are being linked up.
In the case of another known solution, the transmission of the data obtained by the measuring probe is effected acoustically, acoustic signals propagating through the material of the probing rod. The most important drawback of this solution is that the transmitted signal includes a great deal of noise, especially due to machinery, vehicles, etc. present in the vicinity of the probing operation, thus hampering processing and analysis of the measured signals.
It is an aim of the present invention to overcome the abovementioned drawbacks.
The present invention achieves this aim with a soil probing device, wherein each rod section of the probing rod is provided with an optical guide section extending essentially between the ends of the rod section so that linking these rod sections results in the formation of a continuous optical guide within the probing rod.
Surprisingly, the fact that the optical guide is assembled from a plurality of axial sections, with a junction between each section and the next section, is found not to present a problem. This arrangement is found to work even in a very simple embodiment in which the rod sections are attached to one another, for example by means of screw threads, and the heads of the optical guides in those rod sections come to lie close together or against one another without further linking means. Another advantage is that the optical guide itself and the transition of the optical signals from the one guide section to the other guide section are largely insensitive to moisture, in particular much less sensitive than any electrical cable and connections. Given that the probing operation often involves working under damp conditions and below the groundwater level, this is an important practical advantage.
Further advantageous embodiments of the soil probing device according to the invention are described in the following description.